Degassing system for metal alloy furnace



Nov. 2, 1965 y K. c. TAYLOR 3,215,423

DEGASSING SYSTEM FOR METAL ALLOY FURNACE Filed Aug. 1, 1962 3Sheets-Sheet 1 INVENTOR KE/VO/P/C/f C. TAYLOR ATTORNEY Nov. 2, 1965 K.c. TAYLOR DEGASSING SYSTEM FOR METAL ALLOY FURNACE 3 Sheets-Sheet 2Filed Aug. 1, 1962 INVENTOR. Kf/VD/P/C/f C. TAYLOR @Zapz w ATTORNEY Nov.2, 1965 K. c. TAYLOR 3,215,423

DEGASSING SYSTEM FOR METAL ALLOY FURNACE Filed Aug. 1, 1962 I 3Sheets-Sheet 3 Q a, Q s 2 \l r E Q a 1' Q f a 2 c INVENTOR. KE/VDR/CA C.TAVL 0R ATTORNEY 3,215,423 DEGASSING SYSTEM FOR METAL ALLOY FURNACEKendrick C. Taylor, Oreland, Pa., assignor, by mesne assignments, toPennsalt Chemicals Corporation, Philadelphia, Pa., a corporation ofPennsylvania Filed Aug. 1, 1962, Ser. No. 214,031 12 Claims. (Cl.266-34) In general, this invention relates to a new system for applyingchamber degassing to a metal alloy furnace and, more particularly, tothe application of vacuum degassing to electric furnaces.

In the past, vacuum degassing of a molten metal alloy bath wasaccomplished after the alloy had been produced in a furnace. Degassingequipment was placed over a ladle which had received the molten alloyfrom the furnace. This created problems as the molten alloy lost heat inthe transfer between the furnace and the ladle. It has been suggestedthat the loss of heat be rectified by inductively heating the moltenmetal as it moves through a conduit between the ladle and the vacuumchamber. This system of reheating was found to unsatisfactory because itresulted in superheating the molten metal which changed itsmetallurgical properties, was very expensive, and was difficult tocontrol.

Additionally, contamination often occurred in the metal alloy betweenthe transfer from the furnace to the ladle and the degassing therein.The chamber in which the degassing is accomplished requires valuablefloor space in the craneway in a mill which is extremely expensive.Furthermore, since the alloy additive was supplied to the molten metalcharge before it was degassed, elements in the molten metal bath such asoxygen combine with the alloy addition to form undesirable compoundswhich change or damage the metallurgical properties of the resultantalloy metal.

[It is the general object of this invention to avoid and overcome theforegoing and other difiiculties of the prior art practices by theprovision of a better and more simple vacuum degassing system for ametallurgical furnace.

'Another object is to provide a better method of manufacturing metalalloys in which oxides and other contaminates in the molten bath arereduced during vacuum degassing prior to the addition of the alloyingmaterial.

Another object of this invention is to provide a new and novelmetallurgical furnace having an integral vacuum degassing unit attachedthereto.

Another object of this invention is to provide a unitary heater andvacuum degassing chamber combination which may be utilized with aplurality of metallurgical furnace hearths.

Other objects will appear hereinafter.

For the purpose of illustrating the invention there is shown in thedrawings forms which are presently preferred; it being understood,however, that this invention is not limited to the precise arrangementsand instrumentalities shown.

FIGURE 1 is a cross sectional view of an electric arc furnace embodyingthe principles of the present invention. FIGURE 2 is a partial crosssectional view of the furnace of FIGURE 1 taken along lines 22.

FIGURE 3 is a partial cross sectional view of the degassing chambershown in FIGURE 2 taken along lines 3-3.

FIGURE 4 is a top plan view of the electric arc furnace shown in FIGURE1.

FIGURE 5 is a cross sectional view of a second embodiment of the presentinvention.

FIGURE 6 is a cross sectional view of an electric arc furnace with aportable vacuum degassing chamber in United States Patent as to receivethe molten metal charge.

3,215,423 Patented Nov. 2, 1965 ICC accordance with another embodimentof the present invention.

in FIGURE 1, there is shown one embodiment of the present inventionutilized in conjunction with an electric arc furnace. The electric arcfurnace shown in FIG- URE 1 is generally designated by the numeral 10.-

The furnace 10 has a steel outer surface 12 surrounding a refractoryhearth 14. The hearth 14 is shaped so The furnace 10 has a pivotal roof16 through which extend electrodes 24, 26 and 27. The electrodes 24, 26and 27 are adapted to be connected to a three-phase Y-A connectedtransformer. In larger sized electric arc furnaces, six such electrodescould be utilized.

' Metal is placed in the furnace through the open roof or the slidingdoor 18 and is poured from the hearth 14 through a spout 20 on the sideopposite the door 18. The roof 16 is pivotally mounted about an axis '22located on top of the furnace. If necessary, the roof 16 can be pivotedto a position as shown in phantom in FIG- URE 4. In this position, theroof 16 has been numbered 16', and metal can be added to the hearth.

The molten metal 28 is placed at the bottom of the furnace 10 in thehearth 14. A layer of slag 30 forms on top of the molten metal 28. Theslag normally consists of combinations of acid, neutral and basicoxides, and other non-metallics.

{1" he metal 28 is heated by supplying current to the electrodes 24, 26and 27. The electrodes extend into the molten metal 28. The electricalcurrent will strike an are between the electrode and the molten metal28. The slag 30 offers a higher resistance than the molten metal. Thepower input to the electrical arc furnace is controlled by the distancebetween the electrodes and the molten steel. The selected voltage isnormally taken care of by automatic adjustment. The slag, by itspresence, shields the molten metal from the atmosphere and conserves theheat thereof. There is a slight motor or stirring effect produced in thebath by the current, and this also helps in distributing the heat.

The vacuum degassing chamber 44 is provided to be utilized with theelectric arc furnace 10. The vacuum degassing chamber 44 is connectedfrom ports 38 and 40 below the level of molten metal in the hearth 14through pipes 42 and "60 to ports 62 and 64 in the bottom of thedegassing chamber 44. Heater means 43 which may be electric coils or agas burner is provided on chamber 44.

A pump 48 is also in communication with conduit 42 through a pipe 46located below the port 62. An alloy material hopper 50 is also incommunication with the degassing chamber 44 through a port 58 in thewall of the degassing chamber 44. Supply valves '52 and 54 control thefeed of alloy material from the hopper 50. Additionally, a vacuum port66 in communication with the interior of the chamber 44 connects avacuum pump 74 to the chamber 44 through a rigid pipe 68, expansiblebellows 70, and rigid pipe 72.

The operation of the degassing chamber 44 is as follows: The chamber 44is preheated by heater means 43 so that there is little differencebetween the temperature in the furnace and the temperature of thechamber. Vacuum pump 74 evacuates chamber 44 through conduits 68, 70 and72. This causes molten metal to rise in conduits 42 and 60. Pump 48 isthen turned on to supply a gas under pressure through conduit 46. Thisgas may be hydrogen, methane, carbon monoxide, other carbonaceous gases,hydrides, halogens or volatile halides, vapors of strongly reducingvolatile and relatively insoluble metals or metalloids, such as sodiumzinc and phosphorus, inert noble gases, or active gases. The particulargas used depends upon the effect desired upon the molten metal. Forinstance, if it is desired to de-oxidize the molten metal, a reducinggas such as carbon monoxide would be pumped through conduit 46. The gasin conduit 42 lowers the density of the resultant mixture in theconduit. This causes the molten metal in conduit 42 to rise to a higherlevel than the molten metal in conduit 60. Thus, the molten metal actsupon the well-known principle of the gas lift and ultimately overflowsthe top of conduit 42. This action is accentuated by the reducedpressure created by the pump 74.

The gases which have been introduced into the tube 46 bubble upwardlythrough the metal in the conduit 42 and in the course of this operation,they become intimately mixed with the liquid metal. The conduit 42 ispreferably provided with internal turbulence causing projections whichwill insure active mixing and provide a more active flow of the metal.

The gases cause the liquid metal to spill over at the upper end of theriser conduit 42 from which the metal gravitates into the open end 64 ofthe return tube 60. The gases and all other gases which are separatedfrom the metal are then carried away through the vacuum conduit 68, 70and 72 by vacuum pump 74.

The metal which is delivered into the return conduit 60 passesdownwardly into the molten charge 28 through port 38. The conduits 42and 60 form barometric columns which are continuously maintained by thevacuum in the chamber 44.

After the molten metal has been completely treated with the gas from thepump 48, an inert gas such as argon is introduced in place of the activegas, if such was used. The inert gas does not react with the moltenmetal, but instead continues the metal flow through the degassingchamber. At this point, the alloying material which may be silicon,carbon or the like, is fed into the chamber 44 from the hopper 50. Thealloy feeding is done through the use of a trap valve system includingvalves 52 and 54. Valve 52 is first opened with valve 54 closed to placea given amount of alloy material between the two valves. Then valve 52is closed and valve 54 opened and the alloy material allowed to flowinto the chamber 44. The vacuum system will aid in the flow of the alloymaterial into the chamber 44. Since the molten metal is flowingcontinuously in the bottom of the chamber 44, the alloy material will begiven a large surface area to combine with the molten metal.Additionally, since the contaminating gases have been removed from themolten metal, there will be no undesirable chemical reaction betweensuch gases and the alloy mate-rial before the metallurgical combinationwith the molten metal.

The alloying agents which might be utilized could be silicon, chromium,aluminum, manganese, titanium, vanadium, etc. These metals in their pureform can dissolve in the alloy solution without forming contaminatingoxidation by-products. The turbulence of the flowing metal as it leavesport 62 increases the area of contact with the dissolving alloymaterials. An inert gas may be utilized to protect the molten metalcharge at the base of the hearth from contact with the air. This can bedone by the introduction into the furnace of a blanket of gas which isinert to the metal being treated and which is relatively insoluble inthe collected met-a1.

The furnace 10 has two arcuate gear members 32 on the base thereof oneither side of the furnace 10. These arcuate gear members 32 mesh withsimilarly spaced gears 34 fixedly supported on the floor of the mill. A

motor (not shown) drives a connecting arm 36 rotatably secured to thebase of the furnace 10. Movement of the arm 36 causes tilting of thefurnace 10 in one of two directions. When it is necessary to pour themolten metal from the furnace 10,.the connecting arm 36 is moved to theright tilting the furnace and allowing the metal to flow out of spout20. When the slag 30 need be removed, the furnace is tilted in the otherdirection and the door 18 opened so as to allow the slag to be removed.

A new charge of metal can be fed to the furnace through door 18 or byrotating roof 16 to the position indicated in FIGURE 5.

The degassing chamber 44 and hopper 50 are mounted directly on thefurnace 10 and move with it. Vacuum pump 74, however, is mountedseparately and therefore, it is necessary to have the flexible bellows70 which connects the two pipes 68 and 72. Thus, when metal is poured,the bellows contracts and when slag is removed, the bellows expandswithout loss of vacuum.

, -In FIGURE 5, there is shown a second embodiment of the presentinvention. In this embodiment, the furnace has molten metal 82 and slag84 in the bottom thereof. The furnace 80 is also rotatable about curvedgears 86. The furnace 80 has a spout 88 and a gate 90.

A degassing chamber 92 is mounted directly on the roof 108 of thefurnace 80. The roof 108 is removable from the furnace 80. A hopper 94feeds the degassing chamber 92 through a port 96. The vacuum pump 98 isconnected through a flexible conduit 100 to a port 102 in the degassingchamber 92.

Electrodes 104 and 106 are also mounted on the roof 108. Riser tube 112is connected from a point below the level of the molten metal 82 to aport 116 in the chamber 92. A return tube is connected from a port 114lower in level than the port 116 to the molten metal bath 82. A pump 118supplies gas under pressure to riser tube 112.

The operation of the electric arc furnace and degassing unit shown inFIGURE 5 is in all ways similar to that shown in FIGURES 14. However,the unit in FIG- URE 5 has one distinct advantage. In this unit, thedegassing chamber 92 and its auxiliaries may be lifted from the furnace80 and placed on a different furnace while furnace 80 is cleaned andrefilled. Therefore, chamber 92 and its associated apparatus may beutilized by more than one furnace and effect a considerable saving forthe user.

In FIGURE 6, there is illustrated the furnace 10 and a portable vacuumdegassing unit associated therewith for degassing the molten bath 28therein. The unit 130 includes a vacuum chamber 132 having a preheater134. A hopper 136, identical with hopper 50, is associated with thechamber 132. Conduits 138 and 140 extend from chamber 130 into the bath28. The conduits 138 and 140 are parallel to each other and areconnected to chamber 130 in the same manner as conduits 112 and 110,respectively, are connected to chamber 92. Hence, the bath 28 will flowup leg 138 through chamber 132, and down leg 140.

To facilitate introduction of the conduits 138 and 140 in the bath 28,the door 18 on furnace 10 has been moved to an open disposition. Thechamber 132 is mounted on a carriage having wheels 142 and 144 whichride on an inclined track 146. Track 146 is parallel to conduits 138 and140. If desired, an inclined rack and pinions may be substituted for thetrack 146 and wheels 142 and 144. The ends of track 146 are supported bystandards 150 and 152 on platform 148.

A vacuum pump 154 is supported by platform 148. Pump 154 is incommunication with port 158 in chamber 132 by flexible conduit 156. Thechamber 138 is selectively reciprocated along track 146 by a cable 158.One end of cable 158 is secured to chamber 132. Cable 158 extends aroundpulley 160 and is wound on spool 162. Spool 162 is selectively wound orunwound by operating motor 164.

The above mentioned elements of the unit 130 are supported by a portablewheel mounted dolly 166. Platform 148 is adapted to be raised or loweredby hydraulic jacks 168 and 170 and pump 1'72. Dolly 166 is provided withsuitable guides to limit movement of the platform 148 to verticalreciprocation.

Thus, it will be seen that the unit 130 is portable and may be movedfrom furnace to furnace. The jacks 168 and 170 enable the chamber 132 tobe raised or lowered to accommodate the unit to different makes offurnaces. When chamber 132 is at the proper height and supported at thetop of track 146, door 18 is opened. Thereafter, conduits 138 and 140are introduced into the bath 28 by reciprocating chamber 130 towardfurnace 10. Degassing of the bath 28 and addition of alloy metals areaccomplished as set forth above. If desired, unit 130 may be suspendedfrom an overhead track.

The present invention may be embodied in other specific forms withoutdeparting from the spirit or essential attributes thereof and,accordingly, reference should be made to the appended claims, ratherthan to the foregoing specification as indicating the scope of theinvention.

I claim:

1. A method of forming a metal alloy comprising the steps of heatingmetal in a furnace to form a molten metal bath, lifting metal from belowthe surface of the metal bath into a vacuum chamber, feeding alloyagents into the molten metal to form an alloy with the molten metal,returning the metal from the vacuum chamber to a point below the surfaceof the metal bath, and effecting said lifting and returning steps in acontinuous metal flowing cycle, said lifting step including the step offorcing an active gas through the metal to act on the metal, andstopping the forcing of the active gas through the metal prior to thestep of feeding the alloy agents into the metal and forcing an inert gasthrough the metal during the alloy feeding step.

2. The method of forming a metal alloy of claim 1 wherein the step offeeding alloy agents includes the step of measuring a desired amount ofalloy agent in a closed receptacle connected to the vacuum chamber priorto opening the closed receptacle to the vacuum chamber to feed the alloyagents to the molten metal in the vacuum chamber.

3. A metal furnace comprising a hearth for receiving metal to be heated,heating means for heating metal in the hearth, a vacuum degassingchamber spaced from and higher than any metal in the hearth, vacuumdegassing means for circulating metal from said hearth through saidchamber and back to said hearth for degassing the metal, a roof mountedon said hearth, said chamber being mounted on said roof, said vacuumdegassing means including a vacuum pump mounted exterior from saidhearth and roof, and flexible conduit means connecting said vacuum pumpto said chamber.

4. A metal furnace comprising a hearth for receiving metal to be heated,heating means for heating metal in the hearth, a vacuum degassingchamber spaced from and higher than any metal in the hearth, vacuumdegassing means for circulating metal from said hearth through saidchamber and back to said hearth for degassing the metal, a roof on saidhearth, and means for mounting said heating means and said chamber onsaid roof.

5. A metal furnace comprising a hearth for receiving metal to betreated, heating means for heating the metal in the hearth, a vacuumdegassing chamber spaced from and higher than any metal in the hearth,vacuum degassing means for continuously circulating metal from saidhearth through said chamber and back into said hearth for degassing themetal, said last-named means including first and second conduitsconnected to said hearth below the surface of the metal in said hearth,said first and second conduits also being connected to said chamber,said first conduit having its chamber end higher than the chamber end ofsaid second conduit, said vacuum degassing means including a vacuum pumpconnected to said chamber, and a gas supply means connected to saidfirst conduit between said chamber and said hearth.

6. The metal furnace of claim 5 wherein said hearth is arcuately movableto receive and pour out molten metal, said chamber and said conduitsbeing rigidly mounted on said hearth, and said vacuum pump being mountedseparate from said hearth and flexibly connected to said chamber.

7. A metal furnace comprising a hearth for receiving metal to be heated,heating means for heating metal in the hearth, a vacuum degassingchamber spaced from and higher than any metal in the hearth, and vacuumdegassing means for circulating metal from said hearth through saidchamber and back to said hearth for degassing the metal, and meanssupporting said chamber for movement toward and away from said bathalong a linear, inclined path.

8. A furnace in accordance with claim 7 including a pair of conduitscommunicating with said chamber, said conduits having their longitudinalaxis substantially parallel to said inclined path and the ends of saidconduits extending into said bath.

9. A portable degassing unit comprising a movably mounted support frame,a vacuum degassing chamber reciprocably supported by said frame formovement along a linear, inclined path, means for evacuating saidchamber, inlet and outlet conduits communicating with said chamber, saidinlet conduit communicating with said chamber at a point higher than thepoint at which said outlet conduit communicates with said chamber, andthe longitudinal axes of said conduits being substantially parallel tosaid inclined path.

10. A unit in accordance with claim 9 including a preheater for saidchamber for preheating said chamber prior to the introduction of moltenmetal into said chamber.

11. A unit in accordance with claim 9 including a hopper selectivelycommunicating with said chamber and mounted for movement with saidchamber.

12. A unit in accordance with claim 9 including elevating means forraising and lowering said chamber.

References Cited by the Examiner UNITED STATES PATENTS 2,054,922 9/36Betterton et al. 26634 2,528,571 11/50 Babcock et al 26636 X 2,895,8207/59 Harders 7S---48 2,959,478 11/60 Harders 49 3,042,510 7/ 62Armbruster et a1. 7549 FOREIGN PATENTS 837,587 6/60 Great Britain.

JOHN F. CAMPBELL, Primary Examiner.

JAMES A. TAYMAN, JR., MORRIS WOLK, Examiners.

1. A METHOD OF FORMING A METAL ALLOY COMPRISING THE STEPS OF HEATINGMETAL IN A FURNACE TO FORM A MOLTEN METAL BATH, LIFTING METAL FROM BELOWTHE SURFACE OF THE METAL BATH INTO A BACUUM CHAMBER, FEEDING ALOY AGENTSINTO THE MOLTEN METAL TO FORM AN ALLOY WITH THE MOLTEN METAL, RETURNINGTHE METAL FROM THE VACUUM CHAMBER TO A POINT BELOW THE SURFACE OF THEMETAL BATH, AND EFFECTING SAID LIFTING AND RETURNING STEPS IN ACONTINUOUS METAL FLOWING CYCLE, SAID LIFTING STEP INCLUDING THE STEP OFFORCING AN ACTIVE GAS THROUGH THE METAL TO ACT ON THE METAL, ANDSTOPPING THE FORCING OF THE ACTIVE GAS THROUGH THE METAL PRIOR TO THESTEP OF FEEDING THE ALLOY AGENTS INTO THE METAL AND FORCING AN INERT GASTHROUGH THE METAL DURING THE ALLOY FEEDING STEP.
 3. A METAL FURNACECOMPRISING A HEARTH FOR RECEIVING METAL TO BE HEATED, HEATING MEANS FORHEATING METAL IN THE HEARTH, A VACUUM DEGASSING CHAMBER SPACED FROM ANDHIGHER THAN ANY METAL IN THE HEARTH, VACUUM DEGASSING MEANS FORCIRCULATING METAL FROM SAID HEARTH THROUGH SAID CHAMBER AND BACK TO SAIDHEARTH FOR DEGASSING THE METAL, A ROOF MOUNTED ON SAID HEARTH, SAIDCHAMBER BEING MOUNTED ON SAID ROOF, SAID VACUUM DEGASSING MEANSINCLUDING A VACUUM PUMP MOUNTED EXTERIOR FROM SAID HEARTH AND ROOF, ANDFLEXIBLE CONDUIT MEANS CONNECTING SAID VACUUM PUMP TO SAID CHAMBER.